a.lesson(href="#!lessons/" + _id)
    - var tagsList = tags || []
    img.cover(src=fengmian && fengmian.path && ("/r/" + fengmian.path))
    .level=hard
    .lesson-name=name
    .lesson-tags
        each tag in tagsList
            .lesson-tag=tag
    .lesson-author=source
